Snowmobile having electronically controlled lubrication

ABSTRACT

A snowmobile has a frame, an endless drive track, a pair of skis, an engine operatively connected to the endless drive track, an oil tank, an electronic oil pump and an electronic control unit (ECU). The engine has at least one cylinder, a crankcase, and at least one exhaust valve. The electronic oil pump fluidly communicates with the crankcase and the at least one exhaust valve. The oil tank fluidly communicates with an inlet of the electronic oil pump for supplying oil to the electronic oil pump. The electronic oil pump delivers oil from the oil tank to the crankcase and the at least one exhaust valve. The ECU is electrically connected to the electronic oil pump for controlling actuation of the electronic oil pump.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 13/895,759, filed May 16, 2013, which a continuation of U.S.patent application Ser. No. 12/663,986, filed Dec. 10, 2009, now U.S.Pat. No. 8,459,392, issued Jun. 11, 2013, which is a National PhaseEntry of International Patent Application PCT/US2008/055477, filed Feb.29, 2008. Through International Patent Application PCT/US2008/055477,the present application claims priority to U.S. Provisional PatentApplication No. 60/945,709, filed Jun. 22, 2007. The entirety of theseapplications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a snowmobile having electronicallycontrolled lubrication.

BACKGROUND OF THE INVENTION

Snowmobiles conventionally have a lubrication system that uses an oilpump that is mechanically driven by an engine of the snowmobile. Thistype of oil pump is generally referred to as a mechanical oil pump.

When the engine operates on a four-stroke principle, the lubricant isstored in an oil tank that is usually connected or integrated to theengine, such as an oil pan. The mechanical oil pump pumps the lubricantfrom the oil tank to make it circulate through the engine. Aftercirculating through the engine, the lubricant is returned to the oiltank.

When the engine operates on a two-stroke principle, the lubricant isstored in an oil tank that is usually spaced apart from the engine. Themechanical oil pump pumps the lubricant from the oil tank to thecrankcase of the engine. From the crankcase, the lubricant flows to thecylinders where it is combusted with a mixture of fuel and air. Sincethe lubricant is combusted by the engine, the oil tank occasionallyneeds to be refilled with lubricant for the engine to operate properly.

By having the mechanical oil pump driven by the engine, the amount oflubricant being pumped is directly proportional to the speed of theengine. Therefore, the faster the engine turns, the more lubricant isbeing pumped by the mechanical oil pump, and the relationship betweenengine speed and the amount of lubricant being pumped is a linear one.However, the actual lubricant requirements of an engine, especially inthe case of an engine operating on a two-stroke principle, are notlinearly proportional to the engine speed.

Some mechanical oil pumps driven by the engine are also linked to thethrottle lever that is operated by the driver of the vehicle, such thatthe position of the throttle lever adjusts the output of the mechanicaloil pump. Although this provides for an improved supply of lubricant tothe engine, it does not account for other factors which affect theactual lubricant requirements of the engine such as ambient airtemperature and altitude.

For a two-stroke engine, the actual lubricant requirement depends, atleast in part, on the power output of the engine, not engine speed. Thehigher the power output, the more lubricant is required. There areinstances during the operation of the two-stroke engine where the enginespeed is high, but where the power output of the engine is low. In suchinstances, the mechanical oil pump driven by the engine provides a lotof lubricant even though the actual requirements are low. One suchinstance is when the track of the snowmobile is slipping on a patch ofice. In this instance the engine speed is high due to the slippage, butthe actual power output is low. There are other instances where theactual lubricant requirements are lower than what would be provided by amechanical oil pump driven by the engine. For example, at start-up, allof the lubricant that was present in the engine when it was stopped hasaccumulated at the bottom of the crankcase. The accumulated lubricantwould sufficient to lubricate the engine for the first few minutes ofoperation, however the mechanical oil pump, due to its connection to theengine, adds lubricant regardless. Therefore, in the case of an engineoperating on the two-stoke principle, using a mechanical oil pumpresults in more lubricant being consumed by the engine than is actuallyrequired. This also results in a level of exhaust emissions that ishigher than a level of exhaust emissions that would result fromsupplying the engine with its actual lubricant requirements since morelubricant gets combusted than is necessary.

The actual lubricant requirements of an engine for a snowmobile are alsoa function of one or more of the altitude at which the snowmobile isoperating, the engine temperature, and the position of the throttlelever, to name a few. Since snowmobiles are often operated inmountainous regions and that temperatures can vary greatly during thewinter, the actual lubricant requirements of the engine can besignificantly affected by these factors and therefore need to be takeninto account. Conventional snowmobile lubrication systems usingmechanical oil pumps, due to the linear relationship between the enginespeed and the amount of lubricant being pumped, cannot take these intoaccount.

In the prior art, mechanisms were provided on some snowmobiles whichwould modify the amount of lubricant provided by the oil pump per enginerotation. These mechanisms provided two (normal/high, or normal/low) orthree (normal/high/low) oil pump settings. Although these settingsprovided some adjustment in the amount of lubricant being provided tothe engine by the oil pump, since the pump is still mechanicallyconnected to the engine, the relationship is still a linear one, andthus does not address all of the inconveniences described above. Thesettings simply provide consistently more or less lubricant, as the casemay be, than at the normal settings.

Therefore, there is a need for a snowmobile having a lubrication systemthat provides an engine of the snowmobile with an amount of lubricantthat is at or near the actual lubricant requirements of the engine.

There is also a need for a snowmobile having a lubrication system thatsupplies lubricant to an engine of the snowmobile non-linearly withrespect to the engine speed and other factors.

Also, since a mechanical oil pump in snowmobiles is driven by theengine, the power required by the engine to drive the pump cannot beused to drive the track of the snowmobile.

Therefore, there is a need for a snowmobile having a lubrication systemthat requires less power from the engine than would be necessary todrive a conventional mechanical oil pump.

Finally, since snowmobiles are used during the winter, the ambienttemperature can occasionally be low enough that the lubricant becomestoo viscous to be efficiently pumped.

Therefore, there is also a need for a snowmobile having a lubricationsystem that can pump lubricant at low temperatures and for a method ofoperating the lubrication system.

SUMMARY OF THE INVENTION

It is an object of the present invention to ameliorate at least some ofthe inconveniences present in the prior art.

In one aspect, embodiments of the present technology provide asnowmobile having a frame. The frame has an engine compartment, and atunnel rearward of the engine compartment. The snowmobile also has anendless drive track disposed below the tunnel for propelling thesnowmobile, a pair of skis operatively connected to the frame and anengine disposed in the engine compartment. The engine is operativelyconnected to the endless drive track. The engine has at least onecylinder, a crankcase connected to the at least one cylinder, and atleast one exhaust valve connected to the at least one cylinder. Anelectronic oil pump fluidly communicates with the crankcase and the atleast one exhaust valve. An oil tank fluidly communicates with an inletof the electronic oil pump for supplying oil to the electronic oil pump.The electronic oil pump delivers oil from the oil tank to the crankcaseand the at least one exhaust valve. An electronic control unit (ECU) iselectrically connected to the electronic oil pump for controllingactuation of the electronic oil pump.

In some embodiments of the present technology, the engine also has acrankshaft supported by at least one crankshaft bearing. The electronicoil pump fluidly communicates with the at least one crankshaft bearingto supply oil to the at least one crankshaft bearing.

In some embodiments of the present technology, the at least one cylinderis a pair of cylinders and the at least one exhaust valve is a pair ofexhaust valves. The electronic oil pump has a pair of outlets. Each oneof the pair of outlets fluidly communicates with a corresponding one ofthe pair of exhaust valves.

In some embodiments of the present technology, the pair of outlets is afirst pair of outlets. The electronic oil pump has a second pair ofoutlets. Each one of the second pair of outlets fluidly communicateswith a corresponding one of the pair of cylinders.

In some embodiments of the present technology, each outlet of the secondpair of outlets is larger than each outlet of the first pair of outletssuch that more oil is supplied to the pair of cylinders than to the pairof exhaust valves.

In some embodiments of the present technology, a muffler fluidlycommunicates with at least one exhaust port of the engine. The muffleris disposed to one side of the electronic oil pump. The electronic oilpump is disposed between the engine and the muffler.

In some embodiments of the present technology, a hood and side panelsenclose the engine. The muffler and the electronic oil pump are disposedin an enclosure defined by the hood and the side panels.

In some embodiments of the present technology, a straddle seat isconnected to the frame. The straddle seat is disposed rearward of theelectronic oil pump.

In some embodiments of the present technology, the oil tank is disposedin the engine compartment.

In some embodiments of the present technology, the oil tank is connectedto the frame, and the oil tank is disposed behind the engine.

In some embodiments of the present technology, a portion of the oil tankis translucent to permit inspection as to a level of lubricant in theoil tank.

In some embodiments of the present technology, an engine speed sensor isconnected to the engine. The engine speed sensor is electricallyconnected to the ECU for transmitting a signal representative of enginespeed to the ECU. The ECU controls the actuation of the electronic oilpump based at least in part on the signal representative of enginespeed.

In some embodiments of the present technology, the snowmobile has atleast one heat generating component. The electronic oil pump is disposedin proximity to the at least one heat generating component. The at leastone heat generating component is at least one of: a muffler fluidlycommunicating with at least one exhaust port of the engine; a coolanthose fluidly communicating with a cooling system of the engine; and aheat exchanger fluidly communicating with a cooling system of theengine.

In some embodiments of the present technology, the electronic oil pumpis disposed in proximity to the muffler, the coolant hose, and the heatexchanger.

In some embodiments of the present technology, the electronic oil pumpis disposed in proximity to the engine.

In some embodiments of the present technology, the electronic oil pumpincludes a coil.

In some embodiments of the present technology, the electronic oil pumphas at least one outlet angled relative to the inlet of the electronicoil pump. The electronic oil pump is disposed externally of the oil tankand is connected directly to an outlet of the oil tank below the outletof the oil tank.

In some embodiments of the present technology, oil within the oil tankdrains into the electronic oil pump by gravity.

In some embodiments of the present technology, a filter is disposed inthe outlet of the oil tank upstream of the inlet of the electronic oilpump.

In some embodiments of the present technology, the electronic oil pumpincludes at least one piston adapted to reciprocate about an axisperpendicular to the inlet of the electronic oil pump.

Embodiments of the present invention each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presentinvention that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects, and advantages ofembodiments of the present invention will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a right side elevation view of a snowmobile in accordance withthe invention;

FIG. 2 is a perspective view from a front, right side, of an oil tankand electronic oil pump assembly to be used in the snowmobile of FIG. 1;

FIG. 3 is a perspective view from a rear, left side, of the oil tank andelectronic oil pump assembly of FIG. 2;

FIG. 4 is a perspective view from a front, right side, of internalcomponents of the snowmobile of FIG. 1, with some of the componentsremoved for clarity;

FIG. 5 is a perspective view from a rear, right side, of internalcomponents of the snowmobile of FIG. 1, with some of the componentsremoved for clarity;

FIG. 6 is an exploded view of the electronic oil pump used in theassembly of FIG. 2;

FIG. 7 is a perspective view from a rear, left side, of an alternativeembodiment of the electronic oil pump of FIG. 6;

FIG. 8 is a perspective view from a front, right side, of the electronicoil pump of FIG. 7;

FIG. 9 is a schematic illustration of some of the various sensors andcomponents present in the snowmobile of FIG. 1;

FIG. 10 is a logic diagram illustrating a control of the electronic oilpump;

FIG. 11 is a graph illustrating the relationship between the frequencyof operation of the electronic oil pump, engine speed, and throttleopening;

FIG. 12 is a pair of graphs illustrating the relationship between thecurrent being applied to the electronic oil pump, the position of thepump piston, and time;

FIG. 13A is a logic diagram illustrating an alternative control of theelectronic oil pump;

FIG. 13B is a logic diagram illustrating another alternative control ofthe electronic oil pump;

FIG. 14 is a schematic illustration of an alternative embodiment of alubrication system to be used in the snowmobile of FIG. 1; and

FIG. 15 is a schematic illustration of another alternative embodiment ofa lubrication system to be used in the snowmobile of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a snowmobile 10 including a forward end 12 and arearward end 14 which are defined consistently with a travel directionof the snowmobile 10. The snowmobile 10 includes a frame 16 whichincludes a tunnel 18 and an engine compartment 20. A front suspension 22is connected to the frame. The tunnel 18 generally consists of one ormore pieces of sheet metal bent to form an inverted U-shape. The tunnel18 extends rearwardly along the longitudinal centerline 61 of thesnowmobile 10 and is connected at the front to the engine compartment20. An engine 24, which is schematically illustrated in FIG. 1, iscarried by the engine compartment 20 of the frame 16. A steeringassembly (not indicated) is provided, in which two skis 26 arepositioned at the forward end 12 of the snowmobile 10 and are attachedto the front suspension 22 through a pair of front suspension assemblies28. Each front suspension assembly 28 includes a ski leg 30, a pair ofA-arms 32 and a shock absorber 29 for operatively connecting therespective skis 26 to a steering column 34. Other types of frontsuspension assemblies 28 are contemplated, such as a swing-arm or atelescopic suspension. A steering device such as a handlebar 36,positioned forward of a rider, is attached to the upper end of thesteering column 34 to allow the rider to rotate the ski legs 30 and thusthe skis 26, in order to steer the snowmobile 10.

An endless drive track 65 is positioned at the rear end 14 of thesnowmobile 10. The endless drive track 65 is disposed generally underthe tunnel 18, and is operatively connected to the engine 24. Theendless drive track 65 is driven to run about a rear suspension assembly42 for propelling the snowmobile 10. The rear suspension assembly 42includes a pair of slide rails 44 in sliding contact with the endlessdrive track 65. The rear suspension assembly 42 also includes one ormore shock absorbers 46 which may further include a coil spring (notshown) surrounding the individual shock absorbers 46. Suspension arms 48and 50 are provided to attach the slide rails 44 to the frame 16. One ormore idler wheels 52 are also provided in the rear suspension assembly42.

At the front end 12 of the snowmobile 10, fairings 54 enclose the engine24, thereby providing an external shell that not only protects theengine 24, but can also be decorated to make the snowmobile 10 moreaesthetically pleasing. Typically, the fairings 54 include a hood (notindicated) and one or more side panels which can be opened to allowaccess to the engine 24 when this is required, for example, forinspection or maintenance of the engine 24. In the particular snowmobile10 shown in FIG. 1, the side panels can be opened along a vertical axisto swing away from the snowmobile 10. A windshield 56 is connected tothe fairings 54 near the front end 12 of the snowmobile 10.Alternatively the windshield 56 can be connected directly to thehandlebar 36. The windshield 56 acts as a wind screen to lessen theforce of the air on the rider while the snowmobile 10 is moving.

A straddle-type seat 58 is positioned atop the frame 16. A rear portionof the seat 58 may include a storage compartment or can be used toaccommodate a passenger seat (not indicated). Two footrests 60 arepositioned on opposite sides of the snowmobile 10 below the seat 58 toaccommodate the driver's feet.

Turning now to FIGS. 2 and 3, the lubrication system of the snowmobile10 includes an oil tank 70 and an electronic oil pump 72. The oil tank70 is disposed in the engine compartment 20 (see FIG. 4) and is shapedso as to fit between the various other components located in the enginecompartment 20. The oil tank 70 is preferably fixed to the frame 18 andis preferably positioned slightly behind the engine 24. Since the oiltank 70 is not directly connected to the engine 24, the oil tank 70 ispartially isolated from the vibration generated by the engine 24. Theoil tank 70 is preferably made of plastic. As seen in FIG. 3, a portion74 of the oil tank 70 is translucent to permit visible inspection as tothe level of lubricant in the oil tank 70. Level markers 76 provide avisual indication as to the relative level of lubricant in the tank 70.A cap 78 is provided to open or close an oil filling opening (not shown)on the oil tank 70. A hose 80 extends from an upper portion of the oiltank 70 to a component of the engine 24, such as a water pump (notshown), to provide lubricant thereto. When the oil tank 70 is filled upabove the level of the upper end of the hose 80, the hose 80 is filledwith lubricant. The lubricant present in the hose 80 is then graduallyfed by gravity to the component to which the hose 80 is connected. Thevolume of lubricant in the hose 80 is preferably sufficient to providelubricant to the component until the oil tank 70 is once again filled upabove the level of the upper end of the hose 80.

As can also be seen in FIGS. 2 and 3 the electronic oil pump 72 isdisposed externally of the oil tank 70. An inlet 82 of the electronicoil pump 72 is connected directly to a bottom of the oil tank 70 on aside of the oil tank 70 opposite the side of the oil filling opening.The inlet 82 is preferably connected to the lowest point of the oil tank70. The electronic oil pump 72 has four outlets 84, 86. The two outlets84 are connected to hoses 88. As seen in FIG. 4, the hoses 88 areconnected to the two exhaust valves 90 of the engine 24 (one exhaustvalve 90 per cylinder 92.) to supply lubricant thereto. One possibleconstruction of the exhaust valves 90 is described in U.S. Pat. No.6,244,227, issued Jun. 12, 2001, incorporated herein by reference. Itshould be understood that other constructions of the exhaust valves 90are contemplated which would not deviate from the present invention. Thetwo outlets 86 are connected to hoses 94. As seen in FIG. 4, the hoses94 are connected to the crankcase 96 of the engine 24. Each hose 94fluidly communicates with a crank chamber (not shown) inside thecrankcase 96 (one crank chamber per cylinder 92) to supply lubricant tothe crankshaft bearings (not shown) and the other components locatedtherein. It should be understood that should the engine 24 have more orless cylinders 92, that the electronic oil pump 72 would have a numberof outlets 84 and 86 that correspond to the number of cylinders. Forexample, should the engine 24 have three cylinders 92, then theelectronic oil pump 72 would have three outlets 84 and three outlets 86.It is also contemplated that two electronic oil pumps 72 could be usedshould the number of outlets become too great for a single electronicoil pump 72. It is also contemplated that the electronic oil pump 72could provide lubricant only to the cylinders 92 (via the crankcase 96)and that the exhaust valves 90 would be lubricated in some other way. Inthis case, an electronic oil pump 72′ having only two outlets 86 (for anengine 24 having two cylinders 92) as shown in FIGS. 7 and 8 would beused. It is also contemplated that the electronic oil pump 72 couldprovide lubricant to other components and parts of the engine 24.

Turning now to FIGS. 4 and 5, a cooling system, an exhaust system, and apositioning of the electronic oil pump 72 relative to these systems willbe described. The cooling system has a coolant tank (not shown) thatsupplies coolant to the remainder of the system via pipe 98. Coolant canalso flow back to the coolant tank via the pipe 98 when the coolantexpands in the cooling system as the temperature of the coolantincrease. Similarly, gas bubbles in the coolant system can flow to thecoolant tank via pipe 98. Coolant in the system flows in coolant hose100 to T-connector 102, and from T-connector 102 to coolant hose 104.From coolant hose 104, coolant enters coolant passages (not shown)inside the engine 24 thereby absorbing heat from the engine 24. Thecoolant then exits the engine 24 via coolant hose 106. From coolant hose106, the coolant enters a thermostat 108. When the temperature of thecoolant is below a predetermined temperature, the thermostat directs thecoolant back to coolant hose 100, and from there the coolant isre-circulated through the engine 24 as described above. When thetemperature of the coolant is above the predetermined temperature, thethermostat 108 prevents the coolant from entering coolant hose 100 andredirects the coolant to coolant hose 110. It is contemplated that thethermostat 108 could redirect only a portion of the coolant to coolanthose 110 and let a remainder of the coolant flow to coolant hose 100.From coolant hose 110, the coolant flows to a first heat exchanger 112to be cooled. The first heat exchanger 112 forms the upper central partof the tunnel 18. From the first heat exchanger 112, the coolant flowsto coolant hose 114. From coolant hose 114, the coolant flows to asecond heat exchanger 116 (the majority of which is hidden by engine 24in FIG. 4) located in the rear portion of the engine compartment 20 tobe further cooled. It is contemplated that the first and second heatexchangers 112, 116 cooled be located elsewhere on the snowmobile 10 andthat only one of the first and second heat exchangers 112, 116 could beused. From the second heat exchanger 116, coolant flows to coolant hose118. From coolant hose 118, coolant flows to T-connector 102, to coolanthose 104, to the engine 24 to coolant hose 106 and back to thermostat108 as described previously. The thermostat 108 causes the coolant toflow through the first and second heat exchangers 112, 116 until thetemperature of the coolant is once again below the predeterminedtemperature.

The exhaust system receives exhaust gases from the exhaust ports 120(FIG. 4) of the engine 24. The exhaust valves 90 regulate the flow ofthe exhaust gases through the exhaust ports 120. An exhaust manifold(not shown) is connected to the exhaust ports 120. The exhaust gasesflow from the exhaust ports, through the exhaust manifold to a muffler122 (FIG. 5). From the muffler 122 the exhaust gases flow through anexhaust pipe (not shown) to the atmosphere.

As can be seen in FIGS. 4 and 5, the electronic oil pump 72 is disposedin proximity to heat generating components of the snowmobile 10. Theseheat generating components include coolant hoses 110 and 114, heatexchanger 116, muffler 122, and engine 24. The coolant hoses 110 and114, and heat exchanger 116 generate heat due to the hot coolant flowingthrough them. The muffler 122 generates heat due to the hot exhaustgases flowing through it. The engine 24 generates heat due to thecombustion events taking place inside the cylinders 92. The electronicoil pump 72 is located proximate enough to these heat generatingcomponents that the heat generated by them, when the snowmobile 10 is inoperation, heats up the lubricant contained in the electronic oil pump72. Therefore, by being heated, the lubricant maintains a viscositylevel that allows it to be easily pumped by the electronic oil pump 72.It is contemplated that locating the electronic oil pump 72 in proximityto at least one of these heat generating components could be sufficientto maintain the viscosity level of the lubricant in the electronic oilpump 72.

Turning now to FIG. 6, details of the electronic oil pump 72 will bedescribed. The electronic oil pump 72 is what is know as a reciprocatingsolenoid pump. The electronic oil pump 72 has a body 124 having theinlet 82 and the outlets 84, 86 integrally formed therewith. As can beseen, the outlets 86 are larger than the outlets 84. This is becausemore lubricant needs to be supplied to the cylinders 92 by the outlets86 than needs to be supplied to the exhaust valves 90 by the outlets 84.Two O-rings 126 are provided around the outlet 82 to prevent lubricantpresent in the oil tank 70 to seal the connection between the outlet 82and the oil tank 70. A filter 128 is disposed in the outlet 82 toprevent debris from entering the electronic oil pump 72. A stopper 130is inserted in the body 124 centrally of the outlets 84, 86. An O-ring132 disposed around the stopper 130 seals the connection between thestopper 130 and the body 124. Check valves 134 are disposed in thepassage of the outlets 84 to prevent lubricant from entering the body124 via the outlets 84. Similarly, check valves 136 are disposed in thepassage of the outlets 86 to prevent lubricant from entering the body124 via the outlets 86. The check valves 134, 136 are sized according tothe size of their corresponding outlets 84, 86. A piston carrier 138 hasfour pistons 140, 142 thereon. As can be seen the pistons 142 are largerthan the pistons 140. The pistons 142 are used to pump lubricant throughthe larger outlets 86, and the pistons 140 are used to pump lubricantthrough the smaller outlets 84. A spring 144 is disposed between thepiston carrier 138 and the stopper 130. The piston carrier 138 isconnected to a pole 146. An O-ring 148 is provided around the pole 146to prevent lubricant present in the body 124 from leaking into thesection of the electronic oil pump 72 that is opposite the side of thepole 146 where the piston carrier 138 is connected (i.e. to the left ofthe pole 146 in FIG. 6). An armature 150, made of magnetizable materialsuch as iron, is connected to the pole 146. The armature 150 is slidablydisposed inside a sleeve 152. The sleeve 152 is disposed in the centerof a coil bobbin 154. The coil bobbin 154 has a coil 156 (shown indashed lines in FIG. 6) wound around it. The ends of the coil 156 areconnected to connector 158 which is used to connect the electronic oilpump 72 to the electronic control unit (ECU) 160 (FIG. 4). The coilbobbin 154 is disposed inside a solenoid housing 162. A washer 164 isdisposed between the coil bobbin 154 and the end of the solenoid housing162. A spring 166 is disposed between the armature 150 and the end ofthe solenoid housing 162. Three threaded fasteners 168 are used tofastened the solenoid housing 162 to the body 124. When the solenoidhousing 162 is fastened to the body 124, all of the components showntherebetween in FIG. 6, except connector 158, are housed inside thevolume created by the solenoid housing 162 and the body 124.

The electronic oil pump 72 operates as follows. Lubricant enters thebody 124 via inlet 82. Current is applied to the coil 156 via the ECU160, as will be described in greater detail below. The current appliedto the coil 156 generates a magnetic field. The armature 150 slidestowards the body 124 (to the right in FIG. 6) under the effect of themagnetic field. The pole 146 and the pistons 140, 142 move together withthe armature 150. This movement of the armature also causes spring 144to be compressed between the piston carrier 138 and the stopper 130. Themovement of the pistons 140, 142 towards the body 124 compresses thelubricant contained in the body 124 and causes the lubricant to beexpelled from the electronic oil pump 72 through the outlets 84, 86, viathe check valves 134, 136. Once the lubricant has been expelled from theelectronic oil pump 72, the ECU 160, after a certain time delay, stopsapplying current to the coil 156 which then no longer creates a magneticfield. Since the armature no longer applies a force to compress thespring 144, the spring 144 expands, thereby returning the pistons 140,142, the pole 146, and the armature 150 to their initial positions(towards the left in FIG. 6). The spring 166 prevents the armature 150from hitting the end of the solenoid housing 162, which would generatenoise and potentially damage the armature 150, and counteracts the forceof the spring 144 to place the armature 150 in the correct initialposition. By returning to their initial positions, the pistons 140, 142create a suction inside the body 124. The suction 124, along withgravity, causes more lubricant to flow inside the body 124 via the inlet82. The check valves 134, 136 prevent the lubricant that was expelledfrom the electronic oil pump 72 from re-entering the body via outlets84, 86. Once the armature 150 returns to its initial position, the ECU160 applies current to the coil 156 and the cycle is repeated.

It is contemplated that other types of electronic oil pumps could beused. For example, a electronic rotary pump could be used.Alternatively, the armature 150 of the reciprocating electronic oil pump72 described above could be replaced with a permanent magnet. In thisembodiment, applying current in a first direction to the coil 156 causesmovement of the permanent magnet, and therefore of the pistons 140, 142,in a first direction, and applying current in a second direction to thecoil 156 causes movement of the permanent magnet in a second directionopposite the first one. Therefore, by being to control the movement ofthe permanent magnet in both direction, this type of pump providesadditional control over the reciprocating motion of the pump whencompared to the solenoid pump 72 described above.

As described above, the ECU 160 is electrically connected to theconnector 158 of the electronic oil pump 72 to supply current to thecoil 156. The ECU 160 is connected to a power source 161 (FIG. 9) and,based on inputs from one or more of the various sensors described belowwith respect to FIG. 9, regulates when current from the power source 161needs to be applied to the electronic oil pump 72 such that the properamount of lubricant is supplied to the cylinders 92 of the engine 94. Asseen in FIG. 9, an engine speed sensor (RPM sensor) 170 is connected tothe engine 24 and is electrically connected to the ECU 160 to provide asignal indicative of engine speed to the ECU 160. The engine 24 has atoothed wheel (not shown) disposed on and rotating with a shaft of theengine 24, such as the crankshaft (not shown) or output shaft (notshown). The engine speed sensor 170 is located in proximity to thetoothed wheel (see FIG. 4 for example) and sends a signal to the ECU 160each time a tooth passes in front it. The ECU 160 then determines theengine rotation speed by calculating the time elapsed between eachsignal. An air temperature sensor (ATS) 172 is disposed in an air intakesystem of the engine 24, preferably in an air box (not shown), and iselectrically connected to the ECU 160 to provide a signal indicative ofthe ambient air temperature to the ECU 160. A throttle position sensor(TPS) 174 is disposed adjacent a throttle body or carburetor (notshown), as the case may be, of the engine 24 and is electricallyconnected to the ECU 160 to provide a signal indicative of the positionof the throttle plate inside the throttle body or carburetor to the ECU160. An air pressure sensor (APS) 176 is disposed in an air intakesystem of the engine 24, preferably in an air box (not shown), and iselectrically connected to the ECU 160 to provide a signal indicative ofthe ambient air pressure to the ECU 160. A coolant temperature sensor(CTS) 178 is disposed in the cooling system of the engine 24, preferablyin one of coolant hoses 100, 104, or 106, and is electrically connectedto the ECU 160 to provide a signal indicative of the temperature of thecoolant to the ECU 160. It is contemplated that the CTS 178 could beintegrated to the thermostat 108. A counter 180 is electricallyconnected to the ECU 160. The counter 180 can be in the form of a timerand provide a signal indicative of time to the ECU 160. The counter 180could also count the number of times the electronic oil pump 72 has beenactuated. The counter 180 could also be linked to the engine 24 toprovide a signal indicative of the number of rotations of a shaft of theengine 24 to the ECU 160. It is contemplated that the RPM sensor 170could integrate the function of the counter 180 to provide a signalindicative of the number of rotations of a shaft of the engine 24 to theECU 160 in addition to the signal indicative of engine speed. It is alsocontemplated that there could be two (or more) counters 180, one actingas a timer, and the other counting the number of rotations of the engine24 or the number of times the electronic oil pump 72 has been actuated.It is also contemplated that other sensors could be provide, such as forexample an oil type sensor for sensing the type of lubricant placed inthe oil tank 70.

The electronic oil pump 72 has an inherent time delay that is determinedby an elapsed time from the time an electric current is received by theelectronic oil pump 72 from the ECU 160 to the time that lubricant isactually initially expelled from the electronic oil pump 72. Due tomanufacturing tolerances, this time delay varies from one electronic oilpump 72 to the other. Therefore, the electronic oil pump 72 has aspecific time delay 182 associated therewith. The time delay 182 isstored on a computer readable storage medium, such as a bar code or aRFID tag, associated with the electronic oil pump 72. The time delay 182is provided to the ECU 160 and is taken into account when regulating theapplication of current to the electronic oil pump 72 such that theactual operation of the electronic oil pump 72 corresponds to thedesired operation of the electronic oil pump 72 as calculated by the ECU160. An example as to how this is achieved for fuel injectors, and whichcould be adapted for use on electronic oil pumps, is described in U.S.Pat. No. 7,164,984, issued Jan. 16, 2007, the entirety of which isincorporated herein by reference.

Due to manufacturing tolerances, the amount of lubricant being expelledper stroke by the electronic oil pump 72 varies from one electronic oilpump 72 to the other. Therefore, the electronic oil pump 72 has aspecific pump output 183 associated therewith that corresponds to theactual amount of lubricant being expelled per stroke by the electronicoil pump 72. The pump output 183 is stored on a computer readablestorage medium, such as a bar code or a RFID tag, associated with theelectronic oil pump 72. The computer readable storage medium could bethe same as the one used for the time delay 182 or could be a differentone. The pump output 183 is provided to the ECU 160 and is taken intoaccount when regulating the application of current to the electronic oilpump 72 such that the actual operation of the electronic oil pump 72corresponds to the desired operation of the electronic oil pump 72 ascalculated by the ECU 160. It is contemplated that only one of the timedelay 182 and the pump output 183 may be provided for the electronic oilpump 72.

Turning now to FIG. 10, a method of controlling the electronic oil pump72 will be described. The method is initiated at step 200, once theignition key (not shown) is inserted in the snowmobile 10 or once theengine 24 is started. The ambient air temperature (AT) is sensed at step202 by the ATS 172 which sends a signal representative of thetemperature to the ECU 160. At step 204, the ECU 160 compares thetemperature sensed at step 202 to a predetermined temperature (X° C.)below which the increased viscosity of the lubricant (due to the lowtemperature) makes it difficult to initiate pumping. For example, thevalue of X° C. could be −30° C. It should be understood that the actualvalue of X° C. will depend on the properties of the lubricant beingused. If the temperature is not less than X° C., then at step 206 theECU 160 assigns a value of Z milliseconds to the length of time forwhich current is to be applied to the coil 156 during each pumping cycle(t_(ON)). If at step 204 it is determined that the temperature is lessthan X° C., then the ECU 160 looks at the value of the counter 180 atstep 208. For the purposes of FIG. 10, the counter 180 counts the numberof pumping cycles of the electronic oil pump 72. It should be understoodthat the other types of counters 180 described above could also be used.Then at step 210, the ECU 160 compares the count obtained from thecounter 180 to a predetermined value N. If the value of the count atstep 208 is not less than N, which means that electronic oil pump 72 hasbeen operating for a certain period of time, then at step 206 the ECU160 assigns a value of Z milliseconds to the length of time for whichcurrent is to be applied to the coil 156 during each pumping cycle. Ifthe value of the count at step 208 is less than N, which means thatoperation of the electronic oil pump 72 has just begun, then at step 212the ECU 160 assigns a value of Y milliseconds to the length of time forwhich current is to be applied to the coil 156 during each pumpingcycle. The value of Y is greater than the value of Z. This is becausewhen the temperature is below the value X (step 204) and pump operationhas just begun (or is about to begin) (step 210), then the lubricantpresent in the electronic oil pump 72 needs to be heated in order toreduce its viscosity and facilitate pumping thereof. By applying currentto the coil 156 for a longer period of time (Y milliseconds) than wouldnormally be used (Z milliseconds), the coil 156 generates more heat thanit normally would and therefore heats up the lubricant. Once pumping ofthe lubricant has been initiated for a certain number of pumping cycles,then the length of time for which current is to be applied to the coil156 during each pumping cycle can be changed to the shorter period oftime of Z milliseconds even though the air temperature is still low(step 206 from step 210). This is because once lubricant starts flowingthrough the electronic oil pump 72 it becomes easier to pump even thoughits viscosity may be higher than usual. This is also because when theelectronic oil pump 72 has been operating for a certain period of time,then the other components of the snowmobile 10 have also been operatingfor a certain period of time, which means that the heat generatingcomponents previously described now generate sufficient heat to heat thelubricant present in the electronic oil pump 72. Finally, the longerperiod of time (Y milliseconds) for which current is to be applied tothe coil 156 during each pumping cycle is only used for the first fewcycles of the electronic oil pump 72 because it requires more energy(i.e. current applied longer) than is required for the majority of thecycles, and because operating the electronic oil pump 72 in this mannerover a long period of time could generate sufficient heat to damage thecomponents of the electronic oil pump 72.

Once the length of time for which current is to be applied to the coil156 during each pumping cycle has been determined at step 206 or 212, asthe case may be, then the ECU 160 determines the frequency (f) at whichthe electronic oil pump 72 is to be operated. Since the amount of timefor which current is to be applied is known, by determining thefrequency, the amount of time for which current is not to be applied caneasily be determined. To determine the frequency, the speed of theengine 24 is first sensed at step 214 by the RPM sensor 170 which sendsa signal representative of the engine speed to the ECU 160. The throttleposition (TP) is then sensed at step 216 by the TPS 174 which sends asignal representative of the throttle position to the ECU 160. Based onthe signals received from the RPM sensor 170 and TPS 174, the ECU 160calculates, at step 218, a first frequency as a function of engine speedand throttle position. This function is non-linear with respect toengine speed and throttle position as illustrated in FIG. 11. Note thatFIG. 11 is for illustrative purposes only and that the actualrelationship between frequency, engine speed, and throttle position willvary from one type of engine to the other. Then, at step 220, ambientair pressure (AP) is sensed by the APS 176 which sends a signalrepresentative of air pressure to the ECU 160. Based on the signalreceived by the APS 176, the ECU 160 applies at step 222 a correctionfactor to the frequency calculated at step 218. If the air pressure islow (high altitude), then the frequency is decreased since lesslubricant is necessary in these conditions. If the air pressure is high(low altitude), then the frequency is increased since more lubricant isnecessary in these conditions. Then, at step 224, coolant temperature(CT) is sensed by the CTS 178 which sends a signal representative ofcoolant temperature to the ECU 160. Based on the signal received by theCTS 176, the ECU 160 applies at step 226 a correction factor to thefrequency calculated at step 222. If the coolant temperature is high,then the frequency is increased since more lubricant is necessary inthese conditions. If the coolant temperature is low, then the frequencyis decreased since less lubricant is necessary in these conditions. Theat step 228, the ECU 160 determines whether the engine 24 is still inits “break-in” period. The break-in period is the period during which anew engine 24 should not be operated at full capacity. This period cancorrespond to a certain number of hours of operation, a certain numberof kilometres traveled by the snowmobile 10, or a certain number ofengine revolutions. During the break-in period, more lubricant alsoneeds to be supplied to the engine 24 to properly lubricate thecomponents therein. Therefore if at step 228 it is determined that theengine is in its break-in period, the ECU 160 applies at step 230 acorrection factor to increase the frequency calculated at step 226 andthen goes to step 232. If at step 228 it is determined that the engineis not in its break-in period, the ECU 160 then moves directly to step232. The latest frequency that has been calculated before step 232, atstep 230 or 226 as the case may be, corresponds to the desired frequencyof operation of the electronic oil pump 72. As described above, theelectronic oil pump 72 has data associated therewith to take intoaccount the inherent time delay 182 in its operation and/or the actualamount of lubricant being expelled per stroke (pump output 183).Therefore, at step 232, the ECU 160 looks up the pump data (i.e. timedelay 182 and/or pump output 183) of the electronic oil pump 72 andcorrects the desired frequency accordingly at step 234. The frequencycalculated at step 234 corresponds to the frequency at which the ECU 160applies current to the coil 156 (f_(Final)) for a certain period of time(Y or Z milliseconds) such that the pump operates at the desiredfrequency (calculated at steps 226 or 230). From step 234, the ECU 160returns to step 202 and repeats the steps described above. The amount ofcorrection necessary at steps 222, 226, and 230 is based on lookuptables stored in the ECU 160 or a separate electronic storage mediumaccessible by the ECU 160. It is contemplated that rather than applyinga correction factor at steps 222, 226, and 230, that steps 220, 224,228, and 232 could occur between steps 216 and 218, such that at step218 the ECU 160 could calculate the frequency as a function of aplurality of the signals received by the ECU 160, thus eliminating theneed for steps 222, 226, 230, and 234.

Turning now to FIG. 12, a relationship between the current being appliedto the electromagnetic coil 156 of electronic oil pump 72, the positionof the pump pistons 140, 142, and time will be described. Thisrelationship will be described with respect to one cycle of operation ofthe electronic oil pump 72 The cycle time (or the time it takes tocomplete one cycle) is the time from the beginning of one stroke of thepistons 140, 142 to the beginning of the next stroke of the pistons 140,142. At the beginning of the cycle, the electromagnetic coil 156 isconnected to the power source 161 by the ECU 160, current applied to theelectromagnetic coil 156. This causes the pistons 140, 142 to movetowards the body 124 of the electronic oil pump 72. The time it takesthe pistons 140, 142 to move from their initial position (0% strokelength) to the maximum position they can reach (100% stroke length) isknown as the stroke time (t_(STROKE)). As can be seen in FIG. 12, theperiod of time for which current is being applied to the electromagneticcoil 156 (t_(ON)) is longer than the stroke time. This extra amount oftime permits the lubricant in the electronic oil pump 72 to be heated bythe heat generated by the electromagnetic coil 156. During this extraamount of time, the pistons remain in the same position. Theelectromagnetic coil 156 is then disconnected from the power source 161by the ECU 160, such that current is not applied to the electromagneticcoil 156 for a remainder of the cycle (t_(OFF)). This causes the pistons140, 142 to return to their initial position (0% stroke length). Thetime it takes the pistons 140, 142 to return to their initial position(0% stroke length) is known as the return time (t_(RET)). The pistons140, 142 then remain in their initial position until the beginning ofthe next cycle. The way in which t_(ON) is calculated is described inmore detail below, however, in order to maintain proper pump operation,t_(ON) is longer than the stroke time but is preferably less than orequal to the cycle time minus the return time. The stroke and returntimes will depend of the length of the stroke, the force of the springs144, 166, the strength of the magnetic field generated by theelectromagnetic coil 156, and the viscosity of the lubricant beingpumped (which varies with temperature) and are generally determinedexperimentally.

Turning now to FIG. 13A, an alternative method of controlling theelectronic oil pump 72 will be described. The method is initiated atstep 250, once the ignition key (not shown) is inserted in thesnowmobile 10 or once the engine 24 is started. At step 252, the ECU 160limits the maximum engine speed to a value of A RPM, which correspondsto an engine speed limit during normal operation. The ambient airtemperature (AT) is sensed at step 254 by the ATS 172 which sends asignal representative of the temperature to the ECU 160. At step 256,the ECU 160 compares the temperature sensed at step 254 to apredetermined temperature (X° C.) below which the increased viscosity ofthe lubricant (due to the low temperature) makes it difficult toinitiate pumping. For example, the value of X° C. could be −30° C. Itshould be understood that the actual value of X° C. will depend on theproperties of the lubricant being used. If the temperature is less thanX° C., then at step 258 the ECU 160 limits the maximum engine speed to avalue of B RPM which is less than the engine speed limit during normaloperation (A RPM). This is because the increased viscosity of thelubricant at low temperatures would not permit the electronic oil pump72 to operate at a high enough frequency to supply lubricant to theengine if it were to operate above B RPM. From step 258, the method thenproceeds to step 260. If at step 256 it is determined that thetemperature is not less than X° C., then the method proceeds directly tostep 260. At step 260, the frequency (f) of operation of the electronicoil pump 72 is calculated. For example, the frequency could becalculated as in steps 214 to 234 of FIG. 10 described above, but itshould be understood that other ways of calculating the frequency couldbe used. Then at step 262, the cycle time is calculated based on thefrequency calculated at step 260. As would be understood by thoseskilled in the art, the cycle time (in seconds) is equal to one dividedby the frequency (in Hz). It is contemplated that instead calculatingthe cycle time by converting the frequency, that step 260 could beomitted and that the cycle time could be determined directly. Then atstep 264, the speed of the engine 24 is sensed by the RPM sensor 170which sends a signal representative of the engine speed to the ECU 160.At step 266, the ECU 160 compares the engine speed sensed at step 264 toa predetermined engine speed (C RPM), which is less than both A and BRPM. C RPM preferably corresponds to an idle speed of the engine 24. Ifat step 266 it is determined that the engine speed sensed at step 264 isless than C RPM, the t_(ON) to be applied to the electromagnetic coil156 is set to a constant amount of time (D msec). The value of D isselected such that the t_(ON) is longer than the stroke time of theelectronic oil pump 72 regardless of the required frequency of operationbelow C RPM in order to heat the lubricant but that is sufficientlyshort that the power source 161 can supply sufficient current to theelectromagnetic coil 156 to properly operate the electronic oil pump 72.This is because, in a preferred embodiment, the power source 161includes an alternator and the amount of power generated by thealternator is proportional to the engine speed. Therefore, having at_(ON) that is too long at engine speed below C RPM would deplete thepower source and affect the operation of the electronic oil pump 72.From step 268, the method returns to step 260. If at step 266 it isdetermined that the engine speed sensed at step 264 is not less than CRPM, the t_(ON) to be applied to the electromagnetic coil 156 is set toequal a percentage (E %) of the cycle time calculated at step 262. Thispercentage of the cycle time is selected such that t_(ON) is longer thanthe stroke time but is less than or equal to the cycle time minus thereturn time. E % is preferably between 30 and 50 percent of the cycletime. In a preferred embodiment, E % is about 40 percent of the cycletime. Following step 270, the ECU 160 looks at the value of the counter180 at step 272. For the purposes of FIG. 13A, the counter 180 countsthe time for which the engine 24 has been operating above or at C RPM.It should be understood that the other types of counters 180 describedabove could also be used. Then at step 274, the ECU 160 compares thecount obtained from the counter 180 to a predetermined value N. If thevalue of the count at step 274 is greater than N, which means thatelectronic oil pump 72 has been operating for a certain period of timeabove C RPM, then at step 276 the ECU 160 limits the maximum enginespeed to the value of A RPM described above. Therefore, if the maximumengine speed was previously limited to B RPM at step 258, it will now beincreased to be limited to A RPM. This is because by this time thelubricant has been sufficiently heated that the electronic oil pump 72can be operated at the frequency necessary to supply sufficientlubricant to the engine 24 operating at A RPM. From step 276, the methodreturns to step 260. If the value of the count at step 274 is notgreater than N, the method returns to step 260, and the engine speedcontinues to be limited to its previous limit of A or B RPM as the casemay be.

Turning now to FIG. 13B, another alternative method of controlling theelectronic oil pump 72 will be described. Throughout this method, thefrequency (f) of operation of the electronic oil pump 72 is beingcalculated, as in steps 214 to 234 of FIG. 10 described above forexample, but it should be understood that other ways of calculating thefrequency could be used. The cycle time is calculated based on thecalculated frequency. It is contemplated that instead calculating thecycle time by converting the frequency, that the cycle time could bedetermined directly. The method is initiated at step 350, once theignition key (not shown) is inserted in the snowmobile 10 or once theengine 24 is started. At step 352, the ECU 160 resets the counter 180,in this case a time counter, to zero and initiates it, sets the t_(ON)to be applied to the electromagnetic coil 156 to be a constant amount oftime (D msec). The value of D is selected such that the t_(ON) is longerthan the stroke time of the electronic oil pump 72 at engine start-up.Also at step 352, the ECU 160 turns off a low temperature function(LowTLimit), described in greater detail below. The ambient airtemperature (AT) is sensed at step 354 by the ATS 172 which sends asignal representative of the temperature to the ECU 160. At step 356,the ECU 160 determines if at any time during a period of G seconds thetemperature sensed at step 354 is below a predetermined temperature (X°C.) below which the increased viscosity of the lubricant (due to the lowtemperature) makes it difficult to initiate pumping. For example, thevalue of X° C. could be −30° C. It should be understood that the actualvalue of X° C. will depend on the properties of the lubricant beingused. If the temperature is greater than or equal to X° C. during thefirst G seconds of operation of the engine 24, the method ends at step358 and normal operation of the oil pump resumes (for example, as insteps 376 to 382 described below). If the temperature at any pointduring the first G seconds of operation of the engine 24 is less than X°C., then at step 360 the ECU 160 turns on a low temperature function(LowTLimit). When the low temperature function is on, the ECU 160controls the engine 24 so as to limit the maximum degree of opening ofthe exhaust valves, limits the maximum engine speed to a value which isless than the engine speed limit during normal operation, and sends asignal to a display cluster (not shown) of the snowmobile 10 such thatthe display cluster provides an indication to the driver of thesnowmobile 10 that the low temperature function is activated. The enginespeed is limited because the increased viscosity of the lubricant at lowtemperatures would not permit the electronic oil pump 72 to operate at ahigh enough frequency to supply lubricant to the engine if it were tooperate at high speeds. From step 360, the method then proceeds to step362 where the speed of the engine 24 is sensed by the RPM sensor 170which sends a signal representative of the engine speed to the ECU 160.At step 364, the ECU 160 compares the engine speed sensed at step 362 toa predetermined engine speed (C RPM). C RPM preferably corresponds to anidle speed of the engine 24. If at step 364 it is determined that theengine speed sensed at step 362 is less than or equal to C RPM, thet_(ON) to be applied to the electromagnetic coil 156 is set to aconstant amount of time (D msec) at step 366. The value of D is selectedsuch that the t_(ON) is longer than the stroke time of the electronicoil pump 72 regardless of the required frequency of operation below orat C RPM in order to heat the lubricant but that is sufficiently shortthat the power source 161 can supply sufficient current to theelectromagnetic coil 156 to properly operate the electronic oil pump 72.From step 366, the method returns to step 362. If at step 364 it isdetermined that the engine speed sensed at step 362 is greater than CRPM, the t_(ON) to be applied to the electromagnetic coil 156 is set toequal a percentage (E %) of the cycle time at step 368. This percentageof the cycle time is selected such that t_(ON) is longer than the stroketime but is less than or equal to the cycle time minus the return time.E % is preferably between 30 and 50 percent of the cycle time. In apreferred embodiment, E % is about 40 percent of the cycle time.Following step 368, the ECU 160 looks at the value of the counter 180 atstep 370. For the purposes of FIG. 13B, the counter 180 counts the timefor which the engine 24 has been operating above C RPM. It should beunderstood that the other types of counters 180 described above couldalso be used. Then at step 372, the ECU 160 compares the count obtainedfrom the counter 180 to a predetermined value N. If the value of thecount at step 372 is not greater than N, the method returns to step 362.If the value of the count at step 372 is greater than N, which meansthat electronic oil pump 72 has been operating for a certain period oftime above C RPM, then at step 374 the ECU 160 turns off the lowtemperature function. This means that the maximum degree of opening ofthe exhaust valves is no longer limited, that the maximum engine speedto a value is back to the engine speed limit during normal operation,and that the display cluster no longer provides an indication to thedriver of the snowmobile 10 that the low temperature function isactivated (or provides an indication that it is not activated). This isbecause by this time the lubricant has been sufficiently heated that theelectronic oil pump 72 can be operated at the frequency necessary tosupply sufficient lubricant to the engine 24 operating at any enginespeed. From step 374, the method proceeds to step 376 where the ECU 160compares the engine speed sensed at step 376 to the predetermined enginespeed (C RPM). If at step 378 it is determined that the engine speedsensed at step 376 is less than or equal to C RPM, the t_(ON) to beapplied to the electromagnetic coil 156 is set to the constant amount oftime of D msec at step 382. If at step 378 it is determined that theengine speed sensed at step 376 is greater than C RPM, the t_(ON) to beapplied to the electromagnetic coil 156 is set to a constant amount oftime of H msec which is greater than D msec at step 380. From steps 380and 382, the method returns to step 376 and repeats steps 376 to 382until the engine 24 is stopped.

Turning now to FIGS. 14 and 15, alternative embodiments of a lubricationsystem to be used in the snowmobile 10 will be described. Thelubrication systems in FIGS. 14 and 15 both include an oil tank 70, anoil pump 300 fluidly connected to the oil tank 70 for supplyinglubricant to the engine 24 via oil lines 302, and an electronic valve304 fluidly connected to the oil lines 302 downstream of the oil pump300. The number of oil lines 302 preferably corresponds to the number ofcylinders of the engine 24, in this case two. The oil pump 300 ispreferably a mechanical oil pump driven by the engine 24 as is known inthe prior art. It is contemplated that an electronic oil pump and othertypes of pumps could also be used. The electronic valve 304 preferablyincludes an electromagnetic coil 305 to which current can be applied toactuate the valve 304. The electronic valve 304 controls the amount oflubricant being supplied to the engine 24 by redirecting excesslubricant being supplied by the oil pump 300 to an oil by-pass line 306.The oil by-pass line 306 returns the lubricant therein upstream of theoil pump 300 as shown. Alternatively, the oil by-pass line 306 couldreturn the lubricant therein back to the oil tank 70 (see line 306′ inFIGS. 14 and 15). The ECU 160 determines the amount of lubricant thatneeds to be redirected based at least in part from a signal receivedfrom the RPM sensor 170. The ECU 160, which is electrically connected tothe electronic valve 304, then applies current from a power source tothe electronic valve 304 to adjust the valve's position accordingly. TheECU 160 controls movement of the electronic valve between one or morepositions where at least a portion of the lubricant flowing in the oillines 302 is returned to the oil pump 300 via the by-pass oil line 306and a position where the lubricant flowing in the oil lines 302 iscompletely delivered to the engine 24. It is contemplated that the ECU160 could also determine the amount of lubricant that needs to beredirected to the oil by-pass line 306 in a manner similar to the way inwhich the frequency of operation of the electronic oil pump 72 wasdetermined in FIG. 10 above. In the embodiment shown in FIG. 14, theelectronic oil valve 304 is disposed in series with the oil lines 302.In the embodiment shown in FIG. 15, the electronic oil valve 304 isdisposed in parallel with the oil lines 302. It is contemplated that oneelectronic oil valve 304 could be provided for each oil line 302.

Modifications and improvements to the above-described embodiments of thepresent invention may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present invention is therefore intended to be limitedsolely by the scope of the appended claims.

What is claimed is:
 1. A snowmobile comprising: a frame, the frameincluding: an engine compartment; and a tunnel rearward of the enginecompartment; an endless drive track disposed below the tunnel forpropelling the snowmobile; a pair of skis operatively connected to theframe; an engine disposed in the engine compartment, the engine beingoperatively connected to the endless drive track, the engine comprising:at least one cylinder; a crankcase connected to the at least onecylinder; and at least one exhaust valve connected to the at least onecylinder; an electronic oil pump having an inlet, the electronic oilpump fluidly communicating with the crankcase and the at least oneexhaust valve; an oil tank fluidly communicating with the inlet of theelectronic oil pump for supplying oil to the electronic oil pump, theelectronic oil pump delivering oil from the oil tank to the crankcaseand the at least one exhaust valve; and an electronic control unit (ECU)electrically connected to the electronic oil pump for controllingactuation of the electronic oil pump.
 2. The snowmobile of claim 1,wherein: the engine further comprises a crankshaft supported by at leastone crankshaft bearing; and the electronic oil pump fluidly communicateswith the at least one crankshaft bearing to supply oil to the at leastone crankshaft bearing.
 3. The snowmobile of claim 1, wherein: the atleast one cylinder is a pair of cylinders; the at least one exhaustvalve is a pair of exhaust valves; the electronic oil pump has a pair ofoutlets, each one of the pair of outlets fluidly communicates with acorresponding one of the pair of exhaust valves.
 4. The snowmobile ofclaim 3, wherein: the pair of outlets is a first pair of outlets; andthe electronic oil pump has a second pair of outlets, each one of thesecond pair of outlets fluidly communicates with a corresponding one ofthe pair of cylinders.
 5. The snowmobile of claim 3, wherein each outletof the second pair of outlets is larger than each outlet of the firstpair of outlets such that more oil is supplied to the pair of cylindersthan to the pair of exhaust valves.
 6. The snowmobile of claim 1,further comprising a muffler fluidly communicating with at least oneexhaust port of the engine, the muffler being disposed to one side ofthe electronic oil pump, and the electronic oil pump being disposedbetween the engine and the muffler.
 7. The snowmobile of claim 5,further comprising a hood and side panels enclosing the engine; andwherein the muffler and the electronic oil pump are disposed in anenclosure defined by the hood and the side panels.
 8. The snowmobile ofclaim 1, further comprising a straddle seat connected to the frame; andwherein the straddle seat is disposed rearward of the electronic oilpump.
 9. The snowmobile of claim 1, wherein the oil tank is disposed inthe engine compartment.
 10. The snowmobile of claim 1, wherein the oiltank is connected to the frame, and the oil tank is disposed behind theengine.
 11. The snowmobile of claim 1, wherein a portion of the oil tankis translucent to permit inspection as to a level of lubricant in theoil tank.
 12. The snowmobile of claim 1, further comprising an enginespeed sensor connected to the engine, the engine speed sensor beingelectrically connected to the ECU for transmitting a signalrepresentative of engine speed to the ECU; wherein the ECU controls theactuation of the electronic oil pump based at least in part on thesignal representative of engine speed.
 13. The snowmobile of claim 1,further comprising at least one heat generating component; wherein theelectronic oil pump is disposed in proximity to the at least one heatgenerating component; wherein the at least one heat generating componentcomprises at least one of: a muffler fluidly communicating with at leastone exhaust port of the engine; a coolant hose fluidly communicatingwith a cooling system of the engine; and a heat exchanger fluidlycommunicating with a cooling system of the engine.
 14. The snowmobile ofclaim 13, wherein the electronic oil pump is disposed in proximity tothe muffler, the coolant hose, and the heat exchanger.
 15. Thesnowmobile of claim 13, wherein the electronic oil pump is disposed inproximity to the engine.
 16. The snowmobile of claim 1, wherein theelectronic oil pump includes a coil.
 17. The snowmobile of claim 1,wherein: the electronic oil pump has at least one outlet angled relativeto the inlet of the electronic oil pump; and the electronic oil pump isdisposed externally of the oil tank and is connected directly to anoutlet of the oil tank below the outlet of the oil tank.
 18. Thesnowmobile of claim 1, wherein oil within the oil tank drains into theelectronic oil pump by gravity.
 19. The snowmobile of claim 18, furthercomprising a filter disposed in the outlet of the oil tank upstream ofthe inlet of the electronic oil pump.
 20. The snowmobile of claim 1,wherein the electronic oil pump includes at least one piston adapted toreciprocate about an axis perpendicular to the inlet of the electronicoil pump.